The present invention relates to the field of latching mechanisms for doors of truck trailers, containers, freight cars and the like. More specifically, this invention relates to such latching mechanisms wherein a generally arcuate camming member is disposed at each end of a rotatable vertical lock rod which extends above and below the edges of the door. Each of the cam members is adapted to engage a keeper mounted on the door sill or header.
Latches of this general description are known and are shown, for example, in British Pat. No. 1,249,311, Oct. 13, 1971 to Blair Products S. A., and in U.S. Pat. No. 3,989,289, Nov. 2, 1976 to Ringe; 3,806,173, Apr. 23, 1974 to Sweda; 3,801,146, Apr. 2, 1974 to Donath et al; and 3,134,618, May 26, 1964 to Heimann.
The present invention relates to an improved latching mechanism which is designed so that a positive, or locking moment is applied to cam members on a rotatable lock rod when the cam members are in a closed or locked position in keepers and force is applied outwardly to the door. Outward force might be applied to the door, for example, as the result of a shifting load. Thus, a force against the interior of the door and in an outward or door-opening direction, will tend to rotate each cam member and lock rod in a direction which maintains the cam member in a closed or secured position in the keeper housing. It would also be desirable if the cam member, when in a closed or locked position, would span the interior of the hollow keeper housing to limit racking displacement and outward movement of the door.
Hence, it is an object of the present invention to provide a latching mechanism having a positive torque, i.e. a moment in a locking direction, in response to force applied against the door in an outward direction. It is another object of this invention to provide a latching mechanism which can be adapted to limit racking movement. Yet another object of this invention is to provide a latching mechanism which can be adapted to limit inward and outward door play or movement when the latch is closed. Still another object of this invention is to provide a lock rod having a camming member with positive torque in the closed position but can be used to cam the door closed or open by an operator rotating the lock rod.
These and other objects are achieved by the present invention which includes a camming member disposed at each end of a rotatable lock rod extending vertically above and below the edges of a door of a trailer or container. The camming member has a generally arcuate camming finger which is received within a hollow keeper housing secured to the header or sill. When moving to a closed position, a generally concave inner camming surface of the camming finger engages a camming surface interior of the hollow keeper housing. When closed, the point of tangency of the hollow keeper housing and the generally concave inner camming surface of the camming finger is at a relatively planar portion thereof and at a point such that the line of force resulting from a force against the door in a door opening direction is a distance from the plane parallel thereto and passing through the axis of rotation of the lock rod such that a moment is applied to said rod in a locking direction. The camming member can have an extended back and an extended heel to span the interior of the hollow keeper housing and thereby limit play or movement of the camming member when in the closed position.